In recent years surgeons have come more and more to the use of surgical staples (sometimes referred to as staple sutures), rather than conventional thread sutures, for the closing of wounds or incisions in the skin or fascia of a patient. This is true in part because the use of surgical staples is a far easier procedure. Of even greater importance, however, is the fact that the use of surgical staples is very much faster. Thus, the time required for suturing can be substantially reduced, thereby reducing the length of time the patient must be maintained under anesthesia.
Prior art workers have developed various types of surgical stapling instruments. Many of these surgical stapling instruments are provided with staple carrying cartridges which include the staple forming anvil. In some embodiments, the staples are individually located on a flexible belt. This is taught for example in U.S. Pat. No. 3,650,453 and U.S. Pat. No. 3,837,555. U.S. Pat. No. 3,638,847 teaches a cartridge wherein the staples are located individually and one behind the other on a sawtooth staple-retaining member. In U.S. Pat. No. 3,618,842, the staples are located one above the other and are advanced by a pair of threaded screws. U.S. Pat. No. 4,043,504 teaches a cartridge having a staple feeding track wherein the staples are located one above the other and are advanced by a sinuous spring.
Prior art workers have also developed surgical stapling instruments wherein the staples are located in a tandem row in a more conventional staple feed housing. The forwardmost staple of the housing is caused to be shifted downwardly through a substantially vertical staple guide to an anvil by the staple former. Continued movement of the staple former results in the forming of the staple about the anvil. Such a surgical stapling instrument is taught in U.S. Pat. No. 3,873,016.
More recently, single use, disposable surgical stapling instruments have been devised wherein an anvil plate is provided having a central raised portion adapted to be straddled by a plurality of staples arranged in a tandem row. The downwardly depending legs of the staples are confined between the central raised portion of the anvil plate and adjacent vertical walls which may constitute either a part of the anvil plate or a part of the surgical stapling instrument, itself. The central raised portion of the anvil plate terminates at its forward end in an anvil having a coextensive anvil surface. Such surgical stapling instruments are taught in U.S. Pat. No. 4,109,844 and U.S. Pat. No. 4,179,057. In these surgical stapling instruments, the forwardmost staple of the row thereof, located on the anvil, is contacted by the staple former and is simultaneously formed about the anvil and implanted in the skin or fascia of the patient. While the surgical staple of the present invention is not so limited, it will be described in terms of its use with a disposable surgical stapling instrument of the type taught in the above noted U.S. Pat. No. 4,109,844 and the above noted copending application.
Surgical staples are relatively small and are normally made of metallic wire suitable for use in a surgical environment and of circular cross section. The wire is thin, generally having a diameter in the neighborhood of 0.020 inches.
Wire of circular cross section is used to form the surgical staples for a number of reasons. First of all, such wire is easier to make and is more readily available. It is free of sharp edges, easier to form and is more easily removable from the anvil and the former. The use of circular wire, however, has certain disadvantages. For example, as the staples are advanced along the surgical stapling instrument guide means, the fact that their cross section is circular tends to cause the staples to shift laterally with respect to the guide means. This tends to result in a jamming action between the guide means and the adjacent vertical walls of the surgical stapling instrument. To completely prevent this by spacing the adjacent walls from the guide means by a distance just sufficient to enable the staples legs to pass therethrough, would require the maintaining of tolerances which simply would not be practical, particularly in a disposable surgical instrument.
It has also been determined that the manufacture of surgical staples from wire having a circular cross section tends to promote rotation of the crown portion of the surgical staple prior to and during the forming and implanting thereof. As will be more fully described hereinafter, when this occurs it results in improper forming of the surgical staple.
The present invention is directed to the discovery that these problems can be overcome if the surgical staples are made of wire having four flats formed on its exterior surface at 0.degree., 90.degree., 180.degree. and 270.degree. about its circumference. The wire is formed into surgical staples in such a way that each surgical staple will have a flat extending along the upper surface of its crown portion and along the outsides of its downwardly depending leg portions. The surgical staple will have a diametrically opposed flat extending along the underside of its crown portion and down along the insides of its leg portions. This diametrically opposed pair of upper and lower flats will cooperate with the surgical stapling instrument anvil and staple former to prevent axial rotation of the crown during the forming and implanting of the surgical staple.
The surgical staple will also have a diametrically opposed pair of flats extending along the front and rear surfaces of its crown portion and its downwardly depending leg portions. As the tandem row of surgical staples is caused to travel along the guide means by an appropriate pusher element, adjacent surgical staples will contact each other flat-to-flat, eliminating that camming action caused by a circular cross section which tends to result in lateral shifting of the individual surgical staples on the guide means. In this way, the staple feed is greatly improved, by reducing the friction and tendency to jam caused by lateral shifting of the surgical staples.
It is known in the prior art to provide industrial staples and the like with an upper and lower diametrically opposed pair of flats. The purpose of these flats is to improve feeding of the staples on the arm of the staple manufacturing machine and during the application of glue to the staples to make up strips or "sticks" of staples. It will be understood by one skilled in the art that a glued stick of staples is not characterized by the feed problem described above. Surgical staples, on the other hand, are individual, not being formed into strips or sticks. For use in a surgical environment, each surgical staple must be sterile and free of glue or other foreign material.